Control mechanism for oven burners



May 5, 1953 c. M. MAYER ET AL 2,637,389

CONTROLMECHANISMFOROVENBURNERS Filed Dec. 10, 1951 2 SHEETS--SHEET l N, Char/es P7. Mayer' l? m BY 9 Joh/7 M. Hoff bg @Hm HHM May 5, 1953 c. M, MAYER ET AL 2,637,339

CONTROL MEOHANISM FOR OVEN BURNERS Filed Dec. 10, 1951 2 SHEETS- SHEET 2 70 78 f3 46 29 412 sa) 5g W 59 750% 45 W 5f 52@ 1 5g 22 J9 G2 l 53 -23 5:9 gag* INVENTORS' (War/es M Ma yer BY 9 Joh/7 M. Hoff Patented May 5, 1953 UNITED STATES PATENT CFFICE CNTROL MEGHANISM FUR OVEN BURNERS ossi-ies in. Mayer ma Jaim M. nos, Manssen; Ghio, assignors to The Tappan Stove Company, Mansfield, Ohio, 2li-corporation of Ohio' Application December 10, 1951,' SerialNo.-260,9G5

(C1. 1er- 9) 2 Claims.

rlhis invention relates toa control mechanismr i forcoolting range burners `using gaseous fuel and isa modification of they contr-ol mechanism shown incur :zo-pending application filed December. l0, 1951, Serial No.26-O,904. lt is especially designed and adapted for controlling the operation of oven burners in cooking ranges, and may be used in conjunction with a time control mechanism or independently thereof as desired.

The mechanism of theaforesaid (zo-pending applicationis designed for use With a main gaseous fuel oven burner which is adapted to be ignited by `a constantly burning gaseous oven pilot burner. As long as the oven pilot burner is ignited it is immaterial whether or not the main burner burns-constantly during operation.. It may be extinguished forrsome reason, but it will be promptly re-ignited by the oven pilot burner if fuel is supplied thereto. But if the oven pilot burner is extinguished-for any reason during operation a very dangerous situation sometimes arises. Let us assume that both the oven pilot burner and the main oven burner are extinguished during operation for some reason. Gasy can then flow to thev main burner, but since the oven pilot burner is extinguished the main burner will not be ignited and unburned gas Will accumulate in the oven which may violently explode When an attempt is made to ignite either the mainr or pilot burner. It has been l found by experience that both the pilot burner and the main burnervare frequently extinguished during operation. rThis is sometimes due to a momentary failure of the gas supply or the slamming of the oven door or to various other reasons.

In order tov prevent any accumulation of unburned gas and thus eliminate danger of an explosion therefrom in the event the oven pilot burner is extinguished for any reason during operation a safety control unit by which the sunply of gas to the main burner is automatically cut ori in the eventv the pilot burner is extinguished for any reason during operation is provided.` The apparatus is so constructed and arranged that this safety control unit is also utilized to turn the gas on and offto initiate and terminate operation of the' main oven burner which eliminates thev additional manually operable shut off valve generally usedv in -burner control apparatus ot this-type.

The apparatus includes a main gaseous fuel burner by `which theo-ven in a cooking range is heated. The main burner is adapted to be igtemperature.

nited byy a gaseous fuel oven pilot burner which burns both during operation and non-operation of the maiiburner. During periods of non-operation the supply of gas to the main burner is out off by the safety control unit which is interposed in a conduit between the gas supp-ly manifold and the burners. Duringv operation gas iiows from the manifold into the safety control unit. From the safety control unit gas flows through the main conduit and a standard thermostatically operated oven temperature control valve to the main oven burner.

The safety control unit comprises a control valve which is yieldingly biased to closed position and an electromagnet which when energized is operative to hold the control valve in open position after it has been manually moved from closed to open position, but which is not strong enough to move the control valve from closed to open position. The electromagnet is energized by a multiple thermocouple which is heated by the oven pilot burner and Which generates la minute currentof the order of from 200 to 250 millivolts. To initiate operation the control valve is manually moved from closed to open position and then released after which the electroinagnet holds the valve in open position. Gas can then flow from the manifold to the main burner Where it is ignited by the oven pilot burner. The thermocouple', as long as it is heated' by the oven pilot' burner, maintains the safety' control valve in open position'.V The oven temperature control Valve then regulates the supply of gas to the' main burner so as to maintain the desired oven As long' as the oven pilot burner isY ignited the main burner Will burn normally under the control of the' oven temperature control Valve. But if during operationv the oven pilot burner is extinguished for any reason the thermocouple Will immediately cool and' de-energize the electromagnet which allows the safe; ty control unit to automatically cut off the" supply of gas to the main burner. As an example ofthe manner of operation of the apparatus, let us. assume that during operation the oven pilot burner is suddenly extinguished. The thermocouple Will then immediately cool, allowing the safety control unit to cut off the flow of gas from the manifold to the main burner. The oven pilot burnermust then be manually re'- ignited and, after the thermocouple has heenreheated,` the control valve manually re-open'ed to re-initiate operation of the main burner.

In order to extingush the main burner to terminato operation an interiupter switch in th'e`- circuit between the thermocouple and the safety control valve mechanism is provided. The interruptor switch is yieldingly biased to closed position and When momentarily opened breaks the circuit between the thermccouple the safety control mechanism which de-,energizes the electromagnet and releases the control valve allowing it to cut olf the supply of gas to the main burner and thus terminate operation.

In order to adapt the apparatus for automatic control whereby operation of the main burner is automatically initiated at a predetermined set time and is automatically terminated at a predetermined set later time, a normally open solenoid valve is interposed in the fuel supply conduit between the oven temperature control valve and the main burner and a standard electrically operated time control mechanism which includes a normally open switch in series with the solenoid is provided for actuating the solenoid valve. When used the time control mechanism is set as desired which closes the time control switch and energizes the solenoid, thus closing the solenoid valve and then the control valve is manually opened after which the electromagnet will. hold the control valve in open position. Gas can then flow past the control valve and the oven temperature control valve, but it cannot yet flow to the main burner as the solenoid valve is now closed. At the set time the time control mechanism opens the time control switch which de-energizes the solenoid and opens the solenoid valve. Gas will then flow to the main burner and be ignited by the oven pilot burner, after which the main burner operates as described in connection with manual control until its operation is terminated by the time control mechanism closing the time control switch at the set time. The closing of the time control switch effects the closing of the solenoid valve and cuts off the supply of gas to the main burner. The interrupter switch is then momentarily opened which eifects the closing of the control valve, and the time control mechanism is re-set for manual operation.

In order to heat the therrnocouple sufficiently for it to generate enough current to energize the electromagnet in the safety control mechanism the oven pilot burner must be relatively large, burning enough gas to generate approximately 350 B. t. u. per hour. The oven pilot burner should also be approximately this size to assure that it will always ignite the main burner whenever gas is supplied to the main burner. A constantly burning pilot burner of this size mounted in an oven has two disadvantages. First it is costly to operate and second it objectionably heats up the oven when the oven is not in use. In a well insulated oven a constantly burning pilot burner of this size will maintain the temperature in the oven between 100 F. and 110 F.

In the apparatus of the instant invention we eliminate the disadvantages of the aforesaid mechanism by arranging the oven pilot burner to be ignited only during the time the main oven burner is operating and by providing a constantly burning relatively small auxiliary pilot burner which is operative to ignite the oven pilot burner, but which is too small to heat the thermocouple sumciently for it to generate enough current to energize the electromagnet in the safety control unit. And we also provide an interrupter valve in the safety control unit in addition to the control valve therein. To initiate operation of the main oven burner the control and interrupter valves of the safety control unit are simultaneously manually set in position to supply gas to the oven pilot burner while cutting on the supply of gas to the main burner. The valves are manually held in this position until the oven pilot burner has been ignited by the constantly burning auxiliary pilot burner and has heated the therinocouple sufliciently for it to energize the electromagnet in the safety control unit, after which the valves are released. The electromagnet then holds the control valve in the manually set position and the interruptor valve automati cally returns to its original position after which gas iiows to both the main oven burner and the oven pilot burner. The oven pilot burner then ignites the main burner and both burn together until the operation of the main burner is terminated when both the main oven burner and the oven pilot burner are extinguished. In order to terminate operation the interrupter switch in the therrnocouple circuit is momentarily opened as in the aforesaid co-pending application. This breaks the circuit between the therrnocouple and the electroniagnet and de-energizes the electromagnet. The control valve in the control unit then automatically returns to closed position and cuts ofi the supp-ly of gas to both the main oven burner and the oven pilot valve. The apparatus is then ready for a subsequent use of the ovenif a range is to oe used in a locality where outside current is available we provide an automatic 'time control mechanism which is identical in construction and operation with that shown and described in our aforesaid co-pending application.

rEhe principal object of the invention is to prou vide a simplified control mechanism for gaseous fuel cooking range oven burners which is operative to cut oi the supply of fuel to the oven burner in the event the oven pilot burner by which the oven burner is ignited is extinguished for any reason during operation.

Another object of the invention is to provide in an apparatus of the character described a mechanism which acts as a safety control during operation of the oven burners and as a shut oilr valve during periods of non-operation.

Another object of the invention is to utilize the thermocouple circuit in an apparatus of the character described for maintaining or terminating operation of the burner.

Another object of the invention is to provide an oven burner control mechanism or" the character described in which the amount of gas burned by a constantly burning ignition pilot burner is reduced to a minimum.

Another object of the invention is to provide an oven burner control mechanism, having a constantly burning ignition pilot burner, which is so constructed and arranged that the oven will not be unduly heated up during periods of non-operation thereof.

Another object of the invention is to provide a control apparatus of the character described which may be used in conjunction with a time control mechanism or independently thereof as desired.

Other and more limited objects of the invention will be apparent from the following specification and the accompanying drawings forming a part thereof wherein:

Fig. l is a diagrammatic layout illustrating our improved control mechanism as applied to a cooking range oven burner using gaseous fuel;

Fig. 2 is an enlarged vertical section through the safety control unit showing it in oii or nonoperating position; and

Fign is a view similar to Fig. 2 'showing the safety control unit in the position in `which it iis manually set to initiate operationeel the mai-n oven burner.

Referring 4now to the drawings by reference characters, the numeral l Aindicates a lgaseous fuel main burner which is 'mounted `in or in heating'rclation to a cooking range oven 2. Gaseous 4fuel is'supplied to the burner fl from a -manfold M 'through a conduit 3'. interposed 'in the Iconduit 3 vare a safety control unit generally indicated by the numeral 4, and an oven temperature control valve 5. During operation gas flows from the manifold M through the conduit 3 to the safety control unit I, to be described in detail hereinafter. From the 'safety control unit A the gas flows 4through the conduit 3 and the oven temperature control valve -5 to the burner I. The oven temperature control valve 5 is operative to regulate the arnount of gas flowing to the main burner l lin order tomaintain the oven `at any desired set temperature. The valve 5 is set to any desired temperature by a handle Ii having a pointer I2, which cooperates `with a graduated dial` I3 in front of the valve 5. The valve 5 is controlled according to the temperature setting by a thermostatic. element i4 which is mounted in the oven 2 and is connected to the valve 5 as shown .at l5. The oven temperature control valve E is of standard well known construcl tion. Consequently it is not shown in detail herein. There 'are KVmany diierent. constructions available `any one of which will work equally well herein. Gas is also ,supplied to an oven pilot .burner 1G through a secondary conduit il which extendsbetweenthe control unit l! and the oven pilot burner lli. The oven pilot burner le .is mounted in the-oven .2. adjacentthe rear end oi the mainburner l in position to ignite the burner `l when gas .is supplied thereto. A rrelatively small constantly burningV auxiliary pilot burner lil is. also mounted in the .oven-2 in position to ignite the oven pilot burner it when gas is supplied thereto. After the oven pilot burner I6 has been ignited `by the auxiliary .pilot burner it it in turn ignites the main oven'burner l. Gas is .constantly supplied to the auxiliary pilot burner i9 from thel manifold M through a` small oonduit- 2d. A `multiple thermocouple 2l is mounted position to be heated by a llame from the-pilot burner It and is operative when heated to hold the-safety control unitrll open to supply gas to 'both the main burner l and-the oven pilot burner I6, and when cold to release the safety control unit` so that it automatically closes and cuts off the supply of fuel to the maincven burner Land the oven pilot burner I6.

The oven pilot vburner IG which burns only 4during the .operation of the oven Z-rnust be of `such :size as to burn enough gas to generate approximately B. t. u. per hour in orderto always assure the igniting of the main'burner I therefrom and to heat the thermocouple 2| Asuiiiciently to. generate the required current. The constantly burning auxiliary pilot burner is Vbeing used only to ignite the oven pilot burner it is relatively small generating approximately 50 B. t. u. `per hour `which is not sufficient to -appi'eciably heat up the oven during periods of non-operation thereof.

An electric circuit between the `thermocoiuole 2l andi the safety control unit is established by a copper tube 22' which encloses' an insulated wire 23. The wire 23 is severed between thethermoeouple 2lV and the safety control unit 4 and an interruptor 2t having terminals 25 vand 2B is interposed between 'the severed ends. One of the severed ends of the wire .23 is connected to the terminal 2e and the other severed end is `connected to the terminal 26. A normally closed push button switch 2l is mounted in a casing 28 secured to a plate 29 in the cooking range. The switch 2l, which is yieldingly biased to closed position by a spring '30, comprises the contacts Si and 32 and the bar 33 to which a push button te is connected. Theterminal 25 of the interrupterm is connected to the Contact 3l of the vswitch 2l by the lead 23a, and the terminal 2b -oi the interrupter 522i is connected to the contact of the switch 2l by the lead 23h. The purpose and function of the switch 2l will be described hereinafter.

The construction of the safety control valve unit il will now be described, reference being had to Figs. 2 and`3 of the drawings. This 'unit comprises a casing'ii `having a chamber 36 in one end thereof and a chamber 3l in the other end thereof. The chambers 3i andl are connected by a bore 38 of reduced diameter. A valve seat 39 is located at one end of the bore 38 and a similar valve seat 40 is located at the other end of the bore 3S. The chamber 36 is closed by a removable cap el and the chamber 3l is closed by `a removable cap 42. A sleeve t3, having end walls 44 and dii, is carried by the cap il and extends into the chamber 3S; valve stem 46 which is slidably mounted in a bushing l1 carried by the end wall d5 of the sleeve 63, extend-s from the chamber 3&5 into the sleeve 43. A control valve 48 of suitable material is secured to one end of the valve stern i6 within the chamber 36, and an armature fle is secured to the other end ofthe stem fili within the sleeve 43. A spring 50 dis-posed about the valve stem 4b between the valve 48 and the end wall (l5 of the sleeve 43 norm-ally hol-dsthe control valve it against the valve seat 3d. An ele'ctromagnet 5l issecured to one end of a hollow exteriorly threaded stud 52 which extends out through aligned apertures in the end wall All, of the sleeve 53, and in the end of the cap 4l. A nut 53 screwed onto the outer portion of the stud 52 securely holds the magnet 5l and the sleeve 23 in place. The legs of the magnet 5! have a winding 5d thereon one end of which is connected to the tube 22 and the other end of which is connected to the wire 23 in the tube 22. The tube 22 is inserted into the hollow stud 52 and is held in place by a screw tting 52a. A sleeve 55 is screwed into a threaded recess in the end of the cap 32, as indicated at 56, and extends Vinto the chamber 3l a slight distance. One end of the sleeve 55 is closed by an end wall 5l, and the other end which is open registers with a circular aperture 53 in the end wall of the cap` 2. A plunger 5e is slidably mounted in the sleeve 55 and extends out through the aperture 53 in the cap d2. A stem 62 which is secured to the inner end of the plunger 58 eX- ten'ds out' through an aperture G3, in the end wall 5lv o the sleeve 55, andthrough the chamber 31 and into the bore 38. The stem 62 has a collar 'Si rigidly secured thereon between the endwalll''l' and the outer end of the stem. .An interrupt-er valve Eli of suitable material is slidably mounted upon the stem 62 between the end wall 5l of the sleeve 55l and the collar 55.1. The valve' is adapted to engage the valve seat it to cut on the ilow of gas into the chamber 3l' during. the initiation of operation as will be hereinafter described. -A compression spring 66 disposed about the stem 52 between the end wall T and the valve disc 55 normally yieldingly holds the valve 65 against the collar 54. A compression spring 5l which is stronger than the spring 65 is disposed about the stem 52 within the sleeve 55 between the inner face of the end wall 5l and the inner end of the plunger 59. The spring El is operative to return the plunger 59, stem 52 and valve 55 from the position shown in Fig. 3 back to their normal position as shown in Fig. 2, against the resistance of the spring 55. A port 58 in the casing 35 provides communication between the chamber and the conduit 3 to allow gas to flow from the manifold lVl'. through the conduit 3 into the chamber 35. During normal operation of the main burner I gas flows from the chamber 35 through the reduced intermediate bore 35 and into the chamber 3l. A port 59 which establishes communication between the conduits I l and the bore 3B is provided to supply gas to the pilot burner I5; and a port 'l5 establishes communication between the chamber Si and the conduit 3 to permit the flow of gas from the chamber 3l to the main burner i through the oven temperature control valve 5.

Ilhe operation of the appara-tus under manual control will now be described. To initiate operation of the main oven burner i it is only necessary to momentarily manually hold the plunger 59 and then release it. The depressing of the plunger 59 shifts the mechanism of the safety control unit 5 from the position shown in Fig. 2 to the position shown in Fig. 3 to which position gas ows through the conduit Il to the oven pilot burner IG, but is cut oir from the main oven burner l by the interrupter valve 55. The oven pilot burner i5 is then ignited by the constantly burning auxiliary pilot burner IS and heats the thermocouple 2i. As soon as the thermccouple 2! is sufficiently heated, which takes but a few seconds, the plunger 58 is released, it being understood that the plunger must be held depressed until the thermocouple has been sufiiciently heated. As soon as the plunger 55 is released the spring i will return the plunger stem G2, and -interrupter valve 55 back to their original position, as shown in Fig. 2; and the electromagnet 5i being now energized by the thermocouple ZI will retain the control valve in the chamber 35 in open position as shown in Fig. 3. Gas will now flow to the main burner l when it is ignited by the oven pilot burner l5. Under normal conditions the main 'burner I will now operate under control of the oven pilot burner i5 and the oven temperature control f valve 5 until the operation thereof is manually terminated. To terminate operation of the bur-ner i it is only necessary to momentarily depress the push button -ll of the switch 2 which opens the switch El and breaks the circuit between the thermocouple 2i and the winding 55 of the electrcmagnet 5l. The breaking of this circuit de-energizes the electromagnet 55 after which the spring 5d returns the control valve 68 bach from the open position shown in Fig. 3 to the closed| position shown in Fig. 2 which cuts off the supply of gas to both the main burner I and the oven pilot burner I6 and terminates operaion.

Ir" during operation the oven pilot burner i5 is extinguished for any reason and is not immediately reignited by the auxiliary pilot burner I9 the thermocouple 2l will quickly cool and deenergize the electromagnet 5I, after which the spring` 55 will move the control Valve 48 to closed 8 position and cut ofi the supply of gas to both the main burner I and the oven pilot burner I6, thus preventing any possibility of unburned gas escaping into the oven. To re-initiate operation after it has been terminated by the extinguishment of the oven pilot burner I6 the plunger 59 must again be manually depressed as previously described. If for any reason the auxiliary pilot burner i9 is not ignited when the plunger 59 is depressed to initiate operating, operation cannot be initiated since the oven pilot burner I5 must be ignited before gas can be supplied to the main burner I and the oven pilot burner I 6 depends upon the auxiliary pilot burner i9 for ignition. In this case a small amount of unburned gas will escape through the oven pilot burner I 5 into the oven 2 as long as the plunger 5S is held depressed, but this will not be enough to be dangerous las the plunger 59 is only held depressed a few seconds when initiating operation.

In order to adapt the apparatus for automatic control in localities where outside current is available we interpose a normally open solenoid valve 'i5 in the conduit 3 between the oven temperature control valve 5 and the burner i, and we provide a standard electrically operated time control mechanism 'E6 which isv adapted to open and close a switch 'El' at predetermined set times. The switch 'il is mounted in series with a solenoid it which is operative when energized to maintain the normally open valve 'l5 closed.

When used the time control mechanism 'l5 is rst set to initiate operation of the burner I at a predetermined time and to terminate operation thereof at a predetermined later time. The setting of the time control l5 closes the normally open switch Ti which energizes the solenoid I3 which then closes the normally open valve l5. Then the plunger 53 of the safety control mechanism li is momentarily held depressed which opens the control valve in the chamber 35 and supplies gas to the oven pilot burner After the plunger 59 is released the electromagnet 5I, which has been energized by the igniting of the oven pilot burner I5 retains the control valve in open position. Gas `can now flow from the manifold M through the safety control mechanism t, but cannot yet reach the burner I as the normally open Valve l5 in the conduit 3 is now closed. At the set time the time control I5 opens the switch 'll which de-energizes the solenoid 'i8 and opens the valve '55. Gas will now flow to the burner I which is then ignited by the oven pilot burner t5. Under normal conditions the burner i will operate under the control of the oven temperature control valve 5 until at the set time the time control i5 again closes the switch 'll which energizes the solenoid 'i8 and closes the valve 'I5 thus cutting oi the supply of gas to the burner I and terminating operation thereof. The push button switch 6 is then momentarily manually opened which breaks the circuit between the thermocouple 25 and the electromagnet 5! and de-energizes the magnet 5I. The control valve in the chamber 55 is then closed by the spring 55. The time control 'i5 then set for manual control which opens the switch 'Il and de-energizes the solenoid i8 thus opening the valve l5. The apparatus is now ready for the next operation of the burner I.

If during automatic operation the pilot burner I 6 is extinguished for any reason the safety control unit 4 will cut off the supply of gas to the burner I as explained in connection with manual control.

From the foregoing it will be apparent to those skilled in this art that we have provided a very simple and efficient apparatus for accomplishing the objects of the invention.

It is to be understood that we are not limited to the specific construction shown and described herein as various modications may be made therein within the scope of the appended claims.

What is claimed is:

l. In a control apparatus of the character described the combination of a chamber, a fuel supply manifold, a gaseous fuel main burner mounted in said chamber, a fuel supp-ly conduit through which gaseous fuel is supplied to said main burner from said manifold, a relatively large voven pilot burner disposed in said chamber closely adjacent said main burner and operative when ignited to ignite said main burner when fuel is supplied to said main burner, a constantly burning relatively small auxiliary pilot burner disposed in lsaid chamber closely adjacent said oven pilot burner `and operative to ignite said oven pilot burner when fuel is supplied to said oven pilot burner, a safety control unit interposed in said conduit between said manifold `and said main burner, a secondary conduit through which fuel is supplied to said oven pilot burner, a control valve operative when closed to cut off the supply of fuel to said main burner and said oven pilot burner and when open to Iadmit fuel to said main burner and. said oven pilot burner incorporated in sai-d safety control unit, means yieldingly biasing said control valve to closed position, means by which said control valve is manually moved to open position, an electromagnet operative when energized to maintain said control Valve in open position yafter said control Valve has been manually moved to open position incorporated in said safety control unit, a thermocouple mounted in said chamber in position to be heated by said relatively large oven pilot burner, an electric circuit between said thermocouple land said electromagnet through which said electromagnet is energized by said thermocouple when said thermocouple is heated, and a normally closed switch in said electric circuit, said switch being operative when opened to break said circuit and de-energize said electromagnet.

2. In a control apparatus of the character described the combination of a chamber, a fuel supply manifold, a gaseous fuel main burner mounted in said chamber, a fuel supply conduit through which gaseous fuel is supplied to said main burner from said manifold, or relatively large oven pilot burner disposed in said chamber closely adjacent said main burner and operative when ignited to ignite said main burner when fuel is supplied to said main burner, a constantly burning relatively small auxiliary pilot burner disposed in said chamber closely adjagli? cent said oven pilot burner and operative to ignite said oven pilot burner when fuel is supplied to said oven pilot burner, a safety control unit interposed in said conduit between said manifold and said main burner, a secondary conduit through Which fuel is supplied to said oven pilot burner, a control valve operative when closed to cut off the supply of fuel to said main burner and said oven pilot burner and when open to admit fuel to said main burner and said oven pilot burner incorporated in said safety control unit, means yieldingly biasing said control valve to closed position, means by which said control valve is manually moved to open position, an electromagnet operative when energized to maintain said control valve in open position after said control valve has been manually moved to open position incorporated in said safety control unit, a thermocouple mounted in said chamber in position to be heated by said relatively large oven pilot burner, an electric circuit between said thermocouple and said electromagnet through which said electromagnet is energized by said thermocouple when said thermocouple is heated, a normally closed switch in said electric circuit, said switch being operative when opened to break said circuit and deenergize said electromagnet, a normally open valve interposed in said conduit between said safety control unit and said main burnery a solenoid operative when energized to maintain said normally open valve closed, a normally open switch by which the energization of said solenoid is controlled, and a time control mechau nism adapted to be manually set for either manual or automatic control of said main burner, and operative connections between said time control mechanism and said normally open switch through which said normally open switch is opened and closed by said time control mechanism being operative upon the setting thereof for automatic control of said main burner to close said normally open switch and at a predetermined later time to open said normally open switch and at a still later time to close said normally open switch and to again open said normally open switch upon the resetting of said time control mechanism for manual control of said burner.

CHARLES M. MAYER. JOHN M. HOFF.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,353,042 Koch July 4, i944 2,478,386 Ganger Aug. 9, 1949 

